Fire extinguisher discharge horn

ABSTRACT

An improved apparatus and method for discharging carbon dioxide in a fire extinguisher is disclosed. The invention provides a discharge horn having a small inlet orifice for the introduction of carbon dioxide into the horn interior at high velocity. The interior of the horn at the inlet orifice comprises a generally hemispherically shaped diverging nozzle section coaxial with the orifice. The frusto-conical interior of the discharge horn extends outwardly from the nozzle section to the discharge end of the horn. Carbon dioxide gas entering the horn at the inlet orifice is circulated about and fully expanded by the hemispherically shaped diverging nozzle section. The velocity of the carbon dioxide is thus reduced and its turbulence increased. The entrainment of ambient air in the resulting discharge flow of carbon dioxide is thus minimized.

Winston 1 Aug. 26, 1975 FIRE EXTINGUISHER DISCHARGE HORN [75] Inventor: Jack Winston, San Francisco, Calif. Pmrwry b'wmuler M' Henson wood Assistant Exammer-M1chael Mar [73] Assign e Brooks Eq ip n San Attorney, Agent, or FirmTownsend and Townsend Francisco, Calif.

22 Filed: Nov. 1, 1973 1 1 ABSTRACT v An improved apparatus and method for discharging [21] Appl- 411,973 carbon. dioxide in a fire extinguisher is disclosed. The invention provides a discharge horn having a small 169/1 inlet orifice for the introduction of carbon dioxide into 239/499 the horn interior at high velocity. The interior of the [51] Int. Cl. A626. 13/32 horn at the inlet rifice comprises a generally hemi- Field Of Search 169/l 89, 31 spherically shaped diverging nozzle section coaxial 169/ 3; /499 with the orifice. The frusto-conical interior of the discharge horn extends outwardly from the nozzle secl l Reference-S Cited tion to the discharge end of the horn. Carbon dioxide UNITED STATES PATENTS gas entering the horn at the inlet orifice is circulated 2,117,684 5/193x Schaaf 169/30 about l fiflly expanded the hemisPhericauy 2,151.076 3/1939 Bctzlcr 169/30 shaped d1verg1ng nozzle section. The veloc1ty of the 2 545 5 3 951 Frcsc ct a], 1 9 11' carbon dioxide is thus reduced and its turbulence in- 2566324 9/1951 Frcsc 169/11 X creased. The entrainment of ambient air in the result- 2.603,299 7/1 52 Map -W /1 ing discharge flow of carbon dioxide is thus mini- 2.737 251 3/1956 Allen 169 11 mized 3,139.934 7/1964 Gorski 169/31 R 3,204.698 9/1965 Blackman 169/31 R 6 Claims, 3 Drawing Figures FIRE EXTINGUISHER DISCHARGE HORN The present invention relates to fire extinguishers, and in particular to an improved discharge horn for a carbon dioxide fire extinguisher.

The use of portable carbon dioxide fire extinguishers has become increasingly popular since carbon dioxide foam, a mixture of carbon dioxide gas and snow, is a highly effective fire fighter, even against electrical fires where water is ineffective Expanded carbon dioxide gas forms a snow which smothers the fire by cutting off the oxygen required for combustion. However, carbon dioxide fire extinguishers presently available are not as effective as desired because ambient air becomes entrained in the carbon dioxide snow, thus providing oxygen to the fire and reducing the effectiveness of the carbon dioxide snow.

Carbon dioxide is ejected from the storage tank of the extinguisher into the discharge horn at high velocity. The discharge horn of the fire extinguisher is designed to expand the high velocity carbon dioxide to create a mixture of carbon dioxide gas and snow. However, the nozzles used to inject the carbon dioxide into the discharge horn found in the prior art allow for substantial dead zones within the horn. Ambient air from these dead zones is drawn into the high velocity carbon dioxide gas stream and is supplied to the fire. Such nozzles tend to eject the carbon dioxide directly down the center of the discharge horn, setting up a laminar stream of carbon dioxide through the center of the horn. Since the laminar flow stream easily separates from the sidewalls of the horn, ambient air can be drawn into the horn along the sidewalls, and then becomes entrained in the carbon dioxide stream.

lnventors in the past have addressed themselves to the problem of reducing the entrainment of air in the discharge horn of carbon dioxide fire extinguishers. For example, the patent to Mapes, US. Pat. No. 1,967,894, discloses a flat discharge horn having two nozzles in a side-by-side configuration. The patent to Minor, US. Pat. No. 1,760,274, discloses a similar attempt to use multiple nozzles to reduce the entrainment of air. However, these patents do not disclose apparatus which eliminates zones of dead air in the nozzle, but merely fractionate such zones plurality a pluality of smaller zones. These apparatus do not recirculate the carbon dioxide stream to fully expand the gas, and do not introduce turbulence into the stream to prevent the stream from separating from the sidewalls of the discharge horn, and therefore still allow for the entrainment of a substantial amount of ambient air.

SUMMARY OF THE INVENTION The present invention provides a discharge horn for a carbon dioxide fire extinguisher which has an improved nozzle for injecting carbon dioxide into the discharge horn. The nozzle has a generally hemispherical diverging section extending outwardly from the orifice to the interior sidewalls of the horn. Carbon dioxide entering the discharge horn through the orifice is thus recirculated in the hemispherical diverging section of the nozzle. This recirculation eliminates dead zones in the discharge horn near the orifice, expands the carbon dioxide throughout the full cross-section of the horn, and induces turbulence in the carbon dioxide stream.

Expanding the carbon dioxide gas throughout the full cross-section of the discharge horn substantially lowers the velocity of the carbon dioxide stream, enhancing the production of carbon dioxide snow which smothers the fire. The lower velocity stream also has less tendency to entrain ambient air. Elimination of dead zones prevents the formation of a major source of air to be entrained. The introduction of turbulence into the carbon dioxide stream prevents separation of the stream from the sidewalls of the horn to prevent the entrainment of ambient air along the sidewalls of the horn. These factors combine to prevent aggravation of the fire by entrained air in the extinguishing medium, thus increasing the effectiveness of the carbon dioxide extinguisher.

The novel features which are believed to be characteristic of the invention, both as to organization and method of operation, together with further objects and advantages thereof will be better understood from the following description of the drawings in which a preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention.

A BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view of a carbon dioxide fire extinguisher employing the discharge horn of the present invention;

FIG. 2 is a side cross-sectional elevation viewof the discharge horn;

FIG. 3 is an end view of the discharge horn illustrated in FIG. 2.

DESCRIPTION or THE PREFERRED EMBODIMENTS The carbon dioxide fire extinguisher illustrated in FIG. 1 includes a tank portion 10 for containing liquid carbon dioxide under pressure, a valve portion 12 which controls the flow of carbon dioxide from tank 10, a trigger 14 for operating the valve portion, and a discharge horn 16 for expanding and dispensing the carbon dioxide. Discharge horn 16 is constructed of a plastic wh ch does not crack at low temperatures, and is provided with circumferential ridges 18 for added strength A conduit is provided for the passage of carbon dioxide from tank 10 through the valve portion 12 and terminates in an externally threaded nipple 20. Discharge horn 16 has an orifice 22 for passage of the carbon dioxide into the horn. Orifice 22 is internally threaded complementary to nipple 20 so that the discharge horn 16 is conveniently attachable to the nipple.

The discharge horn is illustrated in more detail in the cross-sectional elevation view of FIG. 2 and the end view of FIG. 3. Discharge horn 16 has a nozzle portion 30 by which carbon dioxide, illustrated by arrows 32, enters the interior portion 34 of discharge horn 16.

Carbon dioxide 32 passes through the neck portion 36v of orifice 22 into the diverging portion 38 of nozzle 30. Diverging portion 38 is generally hemispherical, having neck portion 36 of orifice 22 at the center and extendnot precisely hemispherical, being slightly less than half a sphere. Also, it will become apparent that other concave configurations such as hyperbolic could possibly be employed and still achieve the objects of the present invention. However, the term hemispherical will be used herein for simplicity.

Carbon dioxide passing through neck portion 36 of orifice 22 enters the interior portion 34 of discharge horn 16 at the center. However, due to the hemispherical configuration of the diverging portion 38 of nozzle 30, such carbon dioxide is recirculated as illustrated by arrows 40 back into the incoming carbon dioxide stream. In this manner, any potential dead zones, i.e., regions of stagnant air, near orifice 22, are prevented. Instead, entering carbon dioxide 40 is recirculated and expanded throughout the entire diverging portion 38 of nozzle 30.

The interior portion 34 of discharge horn l6 expands the incoming carbon dioxide to transform the carbon dioxide into a mixture of carbon dioxide gas and snow 42. The carbon dioxide snow 42 acts to smother a fire to prevent oxidation and thereby extinguish the flame. Hence, maximizing the formation of carbon dioxide snow maximizes the effectiveness of the extinguisher. The nozzle portion 30 of discharge horn 16 of the present invention acts to fully expand the incoming carbon dioxide throughout the interior portion 34 of horn 16, thereby maximizing the production of carbon dioxide snow. Full expansion of the gas also lowers the velocity of the gas and snow mixture, reducing the tendency to entrain ambient air.

Recirculation of the carbon dioxide gas as illustrated by arrows 40 causes a vortex action which introduces turbulence into the carbon dioxide stream. Since a turbulent boundary layer is less subject to separation from the sidewalls of the discharge horn, the turbulent carbon dioxide gas and snow stream produced by the present invention will not separate which allows for the formation of pockets along the sidewalls of the discharge horn. Prior art devices injected a laminar stream of carbon dioxide gas down the center of the discharge horn, allowing the entrainment of air from dead zones near the nozzle portion and from pockets of air along the sides of the discharge horn. The relatively low velocity, fully expanded, turbulent stream of carbon dioxide snow and gas will thus have a minimum of entrained air.

It is apparent that modifications and adaptations of the present invention will occur to those skilled in the art. In particular, it is obvious that the diverging portion of the nozzle of the present invention could possibly be constructed which is concave but not precisely hemispherical, but would still achieve the objects of the present invention. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present invention, as set forth in the following claims.

What I claim as new is:

l. A method for expanding relatively high velocity carbon dioxide into relatively low velocity carbon dioxide gas and snow comprising the steps of:

injecting the relatively high velocity carbon dioxide into a shaped expansion chamber comprising a discharge hom having a small orifice at one end, a generally hemispherically shaped diverging nozzle section extending outwardly from the orifice, and an outwardly expanding open-ended tapered section contiguous with the nozzle section, said high velocity carbon dioxide being injected into the diverging nozzle section through the orifice;

recirculating the carbon dioxide in the hemispherically shaped diverging nozzle section of the shaped expansion chamber to expand said carbon dioxide into a mixture of carbon dioxide gas and snow, said recirculating increasing the turbulence and lowering the velocity of said carbon dioxide gas and snow; and

dispensing the recirculated carbon dioxide gas and snow from the open end of the tapered section of the expansion chamber, said turbulent, low velocity gas and snow being less subject to entrainment of ambient air.

2. In the horn portion of a carbon dioxide fire extinguisher, said horn portion including a closed end having a small orifice for the introduction of carbon dioxide into the horn at high velocity, and an open end for discharge of carbon dioxide snow and gas at a relatively lower velocity, the improvement wherein the interior of the horn at the closed end comprises a generally hemispherically shaped diverging nozzle section co-axial with the horn, said nozzle section extending outwardly from the orifice at the center of the nozzle section to the interior sidewalls of the horn so that carbon dioxide gas entering the horn from the orifice is expanded and circulated by said diverging nozzle section to reduce the velocity and increase the turbulence of said carbon dioxide.

3. Apparatus for the injection of carbon dioxide gas into the interior of a discharge horn, said apparatus comprising:

a diverging nozzle having concave sidewalls, the outer extremities of said sidewalls being contiguous with and conforming smoothly to the interior walls of the discharge horn; and

an orifice located at the vertex of the diverging nozzle, said orifice adapted to supply carbon dioxide gas at high velocity to said nozzle, said carbon dioxide gas being recirculated by said diverging nozzle to increase the turbulence and lower the velocity of said carbon dioxide.

4. Apparatus as recited in claim 3 wherein the sidwalls of the diverging nozzle are generally hemispherical, the outer extremities of said hemispherical sidewalls being contiguous with and smoothly conforming to the walls of the expansion chamber.

5. A nozzle as recited in claim 3 wherein the orifice has a threaded portion, and additionally comprising conduit means for providing carbon dioxide to said orifice, said conduit means being threadably engageable with said orifice,

6. A carbon dioxide fire extinguisher comprising:

a tank for storage of liquid carbon dioxide under pressure;

conduit means in fluid communication with said tank, said conduit means including valve means for selectively releasing carbon dioxide liquid from the tank through said conduit means, said conduit having an externally threaded end portion; and

an elongate discharge horn having a hollow interior portion for expansion of the carbon dioxide into a carbon dioxide snow and gas mixture, said horn having a closed end provided with an orifice for entry of carbon dioxide into said expansion chamber at high velocity and an open end opposite said and lower the velocity of said carbon dioxide, said orifice having a threaded portion threadably engaged with the end portion of said conduit for selectively providing carbon dioxide to the discharge horn. 

1. A METHOD FOR EXPANDING RELATIVELY HIGH VELOCITY CARBON DIOXIDE INTO RELATIVELY LOW VELOCITY CARBON DIOXIDE GAS AND SNOW COMPRISING THE STEPS OF: INJECTING THE RELATIVELY HIGH VELOCITY CARBON DIOXIDE INTO A SHAPED EXPANSION CHAMBER COMPRISING A DISCHARGE HORN HAVING A SMALL ORIFICE AT ONE END, A GENERALLY HEMISPHERICALLY SHAPED DIVERGING NOZZLE SECTION EXTENDING OUTWARDLY FROM THE ORIFICE, AND AN OUTWARDLY EXPANDING OPEN-ENDED TAPERED SECTION CONTIGUOUS WITH THE NOZZLE SECTION, SAID HIGH VELOCITY CARBON DIOXIDE BEING INJECTED INTO THE DIVERGING NOZZLE SECTION THROUGH THE ORIFICE, RECIRCULATING THE CARBON DIOXIDE IN THE HEMISPHERICALLY SHAPED DIVERGING NOZZLE SECTION OF THE SHAPED EXPANSION CHAMBER TO EXPAND SAID CARBON DIOXIDE INTO A MIXTURE OF CARBON DIOXIDE GAS AND SNOW, SAID ECIRCULATING INCREASING THE TURBULENCE AND LOWERING THE VELOCITY OF SAID CARBON DIOXIDE GAS AND SNOW, AND DISPENSING THE RECIRCULATED CARBON DIOXIDE GAS AND SNOW FROM THE OPEN END OF THE TAPERED SECTION OF THE EXPNSION CHAMBER, SAID TURBULENT, LOW VELOCITY GAS AND SNOW BEING LESS SUBJECT TO ENTRAINMENT OF AMBIENT AIR.
 2. In the horn portion of a carbon dioxide fire extinguisher, said horn portion including a closed end having a small orifice for the introduction of carbon dioxide into the horn at high velocity, and an open end for discharge of carbon dioxide snow and gas at a relatively lower velocity, the improvement wherein the interior of the horn at the closed end comprises a generally hemispherically shaped diverging nozzle section co-axial with the horn, said nozzle section extending outwardly from the orifice at the center of the nozzle section to the interior sidewalls of the horn so that carbon dioxide gas entering the horn from the orifice is expanded and circulated by said diverging nozzle section to reduce the velocity and increase the turbulence of said carbon dioxide.
 3. Apparatus for the injection of carbon dioxide gas into the interior of a discharge horn, said apparatus comprising: a diverging nozzle having concave sidewalls, the outer extremities of said sidewalls being contiguous with and conforming smoothly to the interior walls of the discharge horn; and an orifice located at the vertex of the diverging nozzle, said orifice adapted to supply carbon dioxide gas at high velocity to said nozzle, said carbon dioxide gas being recirculated by said diverging nozzle to increase the turbulence and lower the velocity of said carbon dioxide.
 4. Apparatus as recited in claim 3 wherein the sidwalls of the diverging nozzle are generally hemispherical, the outer extremities of said hemispherical sidewalls being contiguous with and smoothly conforming to the walls of the expansion chamber.
 5. A nozzle as recited in claim 3 wherein the orifice has a threaded portion, and additionally comprising conduit means for providing carbon dioxide to said orifice, said conduit means being threadably engageable with said orifice.
 6. A carbon dioxide fire extinguisher comprising: a tank for storage of liquid carbon dioxide under pressure; conduit means in fluid communication with said tank, said conduit means including valve means for selectively releasing carbon dioxide liquid from the tank through said conduit means, said conduit having an externally threaded end portion; and an elongate discharge horn having a hollow interior portion for expansion of the carbon dioxide into a carbon dioxide snow and gas mixture, said horn having a closed end provided with an orifice for entry of carbon dioxide into said expansion chamber at high velocity and an open end opposite said closed end for discharge of the carbon dioxide snow and gas mixture at a relatively lower velocity, the hollow interior portion of the discharge horn adjacent the orifice being generally hemispherical having the orifice at the center for recirculating the carbon dioxide injected into the expansion chamber through said orifice to increase the turbulence and lower the velocity of said carbon dioxide, said orifice having a threaded portion threadably engaged with the end portion of said conduit for selectively providing carbon dioxide to the discharge horn. 